Subject of this short elaboration is to designate a formula for **capacitance of flat capacitor**. The main reason for obtaining a mathematical formula for capacitance of flat capacitor is that it depends only from geometrical dimensions and material's constants. Flat capacitor's capacitance will be designated with application of following things:

• definition of electrical capacitance

• Gauss's law

• equation for electric flux

• dimensions of flat capacitor

• knowledge of material's constants → relative electrical permittivity and electrical permittivity of vacuum

• knowledge of electrical charge's density per area